**Preface to "Technologies of Coatings and Surface Hardening for Tool Industry"**

The innovative **Coatings and Surface Hardening** technologies developed in recent years allow us to obtain practically any physical–mechanical or crystal–chemical complex property of the metalworking tool surface layer. Today, the scientific approach to improving the operational characteristics of the tool surface layers produced from traditional tools industrial materials is a highly costly and long-lasting process. Different technological techniques, such as coatings (physical and chemical methods), surface hardening and alloying (chemical-thermal treatment, implantation), a combination of the listed methods, and other solutions are used for this. The high efficiency of this approach may be explained by the fact that under the diversified operating conditions of the metalworking tool, in all cases, the most loaded is its surface layer. First, its properties precisely define the workability of the tool piece during the machining of a part. There is no all-purpose coating and surface hardening method; everything is very particular for each type of tool piece and its operating conditions. It should additionally be emphasized that the metalworking tool as an object of research was not chosen accidentally. Production experience shows that even with the most advanced machine tools, it is not possible to achieve high technical and economical rates of the machining process of the part with a low work resource of the tool. Diverse conditions of the tool operation bring on diverse injuries and failures of the technological system. At the same time, the wear rate of the tool is significantly higher than the wear rate of the machine tool parts and units. Therefore, the operational ability of the technological system as a whole depends on the metalworking cutting and die tool used. The roles of the tool multiply when it comes to machining composite materials, high-hardened steels, chrome-nickel, titan, or other hard-to-machine alloys. The scientific school of Moscow State **University of Technology STANKIN** is the leading scientific and educational center in the Russian Federation in the field of the science and technology of the machine-building industry, as well as other science-intensive manufacturing sectors, which introduces traditional and innovative approaches in the educational process for students and experienced specialists, and conducts research activities. The non-interrupted development of projects related to the critical stages of the modern technical progress in **Coatings and Surface Hardening for Tool Industry** by academic staff demonstrates the most current and innovative scientific results, which are published in high-ranking international scientific journals. The years of experience of the team of highly qualified scientists and specialists contribute to developing innovative products and technologies in the tool industry. The most remarkable results of scientific activities in the form of patented technologies, methods, techniques, and equipment are commissioned in the engineering enterprises for producing reliable and high-performance cutting tools. The most recent achievements of the department and invited colleagues in the field of **Tool Coatings and Surface Hardening** are presented in the Special Issue of *Coatings*.

> **Sergey N. Grigoriev** *Editor*
